The report from University of Minnesota researchers finds that TV advertisements in late 2013 and early 2014 were linked to coverage gains under the federal Affordable Care Act (ACA), particularly in states such as Minnesota that ran their own ads.

Researchers can't say whether the Paul Bunyan ads for the MNsure exchange were effective, since they don't have state-specific results. Nor can they prove a causal relationship between the ads and sign-ups.

Even so, the overall findings are significant, researchers say, since the Republican drive to replace the ACA could focus resources on state and private insurance markets.

"The one-sentence message would be: Ads matter," said Pinar Karaca-Mandic, a researcher at the U's School of Public Health.

Sarah Gollust, another U researcher on the study, added: "Any market-based health insurance system like we have in the United States will rely on investment in advertising on TV to attract consumers. Our results would suggest that investment is a good idea."

In late 2013 and 2014, the airwaves were crowded with noise about the ACA. Insurers and new government-run exchanges were pumping out ads to get people interested in coverage under the act, which includes a tax penalty for people who lack health insurance.

MNsure's marketing campaign at the time included about $1.1 million in TV ads featuring the mythical woodsman Paul Bunyan and Babe the Blue Ox. One spot showed Paul suffering an accident while water-skiing, and concluded with the tagline: "Minnesota, Land of 10,000 Reasons to Get Health Insurance."

At the same time, the political wars over the health law were hitting yet another peak as news reports detailed technical problems at MNsure, healthcare.gov and some other state-based exchanges. The websites were meant to be new, consumer-friendly marketplaces where people who buy health insurance on their own could purchase individual policies; the exchanges also direct users to Medicaid coverage when appropriate.

Open enrollment

During the 2013-14 open enrollment, more than 8 million people obtained private coverage through one of the exchange marketplaces while 4.8 million people enrolled in Medicaid, researchers wrote in a study published this month in the journal Health Affairs. To study the effect of ads on sign-up tallies, researchers crossed broadcast television airings data with county-level information from the U.S. Census Bureau on insurance coverage rates in 2013 and 2014.

"We found that counties exposed to higher volumes of local insurance advertisements during the first open enrollment period experienced larger reductions in their uninsurance rates than other counties," researchers wrote. "State-sponsored advertisements had the strongest relationship with declines in uninsurance, and this relationship was driven by increases in Medicaid."

Researchers looked at the volume of news reports and political advertising focused on the health law, but didn't find a similar connection to the number of people signing up for coverage. The study found a stronger sign-up connection to ads sponsored by states that operated their own exchanges, vs. marketing from private health insurers and the federal government's healthcare.gov exchange.

"For every 1,000 advertisements shown, we observed an average decline in uninsurance of 0.1 percentage point," researchers wrote. "Most of these gains in insurance appeared to be driven by the variations in volume of advertisements sponsored by state [exchanges]."

Karaca-Mandic said the calculations yield a "back-of-the-envelope" estimate that about 2.5 people gained coverage for each airing of a state-sponsored ad. She cautioned, however, that the rate of coverage gains per ad might have been unusually high in late 2013 and early 2014, because ACA incentives and penalties were just kicking in. During the time period, private health insurers aired more ads than the government-run exchanges, researchers found, yet the private ads were not associated with insurance gains.

The study wasn't designed to explain why some ads might be more effective than others, but it could be the state ads happened to run in places that reached the target audience, researchers said. Gollust offered another guess based on the time she spent viewing many of the 30-second messages.

"Both the federal healthcare.gov and the state ads all reference how to sign up very explicitly," she said, "whereas some of the private sponsors are just talking about the product of health insurance. ... It could be that the types of ads that were more influential provided that specific information about how to enroll."

Twitter: @chrissnowbeck

Christopher Snowbeck covers health insurers, including Minnetonka-based UnitedHealth Group, and the business of running hospitals and clinics.

The state's technology system has been plagued by high-profile failures, and finding someone willing to head the department has proven challenging. "It keeps me up at night," Walz said in an interview.